Many of the power transmissions in use today have a plurality of stationary torque transmitting mechanisms or brakes which are operated to establish one or more gear ratios in the transmission. Each of the torque transmitting mechanisms has a backing plate that is positioned in a transmission housing by a locating ring and groove structure. The locating ring cooperates with a wall of the groove to determine the axial position of the backing plate when the torque transmitting mechanism is engaged.
In some of the power transmissions, the backing plates are positioned in the housing in axial adjacent relation. In these instances it has been common practice to use a single locating ring to establish the operating position of the backing plates. However, when the torque transmitting mechanisms are engaged and disengaged to control sequential gear ratios, the axial movement of the backing plates can produce a disturbance in the torque transmission during a ratio interchange.
During the ratio interchange, the backing plate of the oncoming torque transmitting mechanism is being urged against the locating ring as the torque capacity of the oncoming torque transmitting mechanism is increasing. However, the backing plate of the offgoing torque transmitting mechanism will also be applying a force to the locating ring that is opposite the force of the oncoming torque transmitting mechanism. Since some assembly tolerance is present between the locating ring and the groove side walls the locating ring will move axially during the ratio interchange as the force balance on the locating ring changes.
This axial movement of the locating ring can disturb the shift timing by effectively increasing the fill time of the oncoming torque transmitting mechanism and prevent the offgoing torque transmitting mechanism from exhausting at the design rate. As a result of the axial movement of the locating ring, the torque transmitting mechanisms can experience excess overlap time during the ratio interchange or reduced capacity of the oncoming torque transmitting mechanism which results in a slight speed flare of the power source. The later of these undesirable episodes can affect the adaptive algorithms of the electronic control system that continually monitors and corrects the ratio interchange timing.